The present invention relates to a device for detecting the rotational behavior of a vehicle wheel, which includes an encoder rotating with the wheel and having permanent magnet areas that are evenly distributed in a circumferential direction and follow one another with alternating polarity, and a stationary measurement transducer sensitive to magnetic fields which furnishes an output signal representative of the rotational movement, and an electric circuit to evaluate the output signals of the measurement transducer.
A device for detecting rotational or angular movements is disclosed in WO 95/17680. The measurement device includes a measurement transducer in the shape of an encoder which rotates with the wheel and has a plurality of permanent magnet areas that are arranged so as to be evenly distributed in the direction of rotation over the entire periphery of the encoder. As a measurement transducer, an active measuring element is arranged stationarily at the periphery of the encoder in such a manner that the variations of the magnetic field which are due to the rotation produce signals at the output of the measuring elements or measurement transducer which indicate the rotation.
Passive and active measurement devices for detecting the rotational behavior of vehicle wheels are numerous and manifold in the state of the art. An electric signal representative of the rotational movement is, among others, required as an input quantity of automotive vehicle control systems, such as antilock systems (ABS), traction slip control systems (TCS), driving stability control systems (DSC, ASMS), etc. The necessary effort in manufacture beside a reliable mode of operation is of major significance for these cases of application, even more so because most of the systems require several sensors, i.e., one individual rotational speed sensor for each vehicle wheel. Therefore, the search for an especially inexpensive sensor is the objective of intensive development work.
An object of the present invention is to develop a measurement device of the type mentioned hereinabove which involves, above all, reduced efforts in manufacture and assembly and ensures a high degree of reliability.